In order to gain access to machine parts located at different distances from the outer surface of the machine, it is essential for an operator to have a tool with a handle (or shank) of sufficient length to reach the machine parts. Handle extensions affixed to a handle of a tool (such as, for example, wrenches) permit an operator to reach machine parts located at distant locations. These handle extensions typically include a sleeve telescopically movable relative to the handle of the tool. The parts can be detented in several positions with respect to each other.
The handle extension is particularly useful for providing increased leverage or torque in the use of the tool.
A variety of handle extensions, and tools with extensible shanks, are disclosed in a number of prior art publications.
For example, U.S. Pat. No. 2,438,633 discloses an extensible tool shank having a cylindrical sleeve and a square cross-sectioned bar longitudinally slidable (but not turnable) in the sleeve. A series of spaced-apart notches along the bar engage with projections on the sleeve for the purpose of adjusting the extension.
U.S. Pat. No. 2,963,930 discloses an extensible torque bar having a cylindrical torque tube with a non-circular internal channel and a torque rod slidably (but non-rotatably) carried in the channel. The torque rod has a series of notches, and a torque tube carries a ball detent which is capable of engaging a respective notch on the torque rod and of being locked therein for the length adjustment.
U.S. Pat. No. 3,227,015 discloses a socket wrench with an extension feature and includes a pair of cylindrical telescoping members capable of being locked in several relative dispositions with respect to another.
U.S. Pat. No. 4,070,932 discloses an extensible handle for a ratchet wrench. The handle includes a cylindrical sleeve which carries the tool headpiece and a cylindrical rod which is telescopically received within the sleeve and is resiliently biased towards an extended position. A latch is provided for locking the rod in a retracted position and in an extended position, respectively.
U.S. Pat. No. 4,581,958 discloses an extensible handle assembly for a ratchet wrench or the like, which includes a cylindrical handle member and a tool shank extended internally within the handle member. The shank is slidable in the handle member between extended and retracted positions. The handle member has a spring-biased-ball to engage the shank at each of these positions.
U.S. Pat. No. 5,109,737 discloses a ratchet wrench having a cylindrical sleeve slidable and rotatable on the handle of the ratchet. The sleeve is provided with a plurality of holes to receive a detent affixed to the handle for positioning the sleeve.
U.S. Pat. No. 5,396,820 discloses an open end wrench with an extensible handle, which has a primary handle over which an extension may be slid to various positions for increasing or decreasing the torque applied to the tool. The primary handle is provided with a plurality of notches while the extension has a thumb press which engages a respective notch for adjusting the handle extension.
U.S. Pat. No. 5,471,899 discloses a ratchet wrench with a handle extension feature, which includes an inner shaft (which is a handle of the wrench) provided with aligned lock pin holes therealong. An outer cylindrical sleeve is mounted telescopically and fits snugly about the inner shaft for axial movement relative thereto. At its proximal end, the sleeve carries a pair of lock pins which engage respective lock pin holes on the inner shaft for the purpose of adjusting the handle length.
In all of the above-described prior art handle extensions for wrenches (and the like) the shank or handle of the tool must be modified to provide a certain detent means cooperating with a slidable extension member telescopically mounted on the handle. This required modification of the tool handle may be undesirable since, first, it is an extra element of manufacturing cost and, second, it creates localities of additional stress in the shank which can dilute its structural integrity and precipitate a product failure.
Therefore, it would be very desirable if the handle extension would not require any secondary machining or rework of the tool handle, nor add unnecessary manufacturing cost, and yet would be comfortable to use and preserve the structural integrity of the tool handle.